The present invention relates to a multiplex type transmitting apparatus which is arranged to hold various kinds of transmission synchronous systems of an SDH (Synchronous Digital Hierarchy) and a SONET (Synchronous Optical Network).
The conventional synchronous digital transmitting systems include a SONET synchronous transmitting system defined on the ANSI T1.105 and an SDH synchronous transmitting system defined on the ITU-TG.707 (1995).
For both of these transmitting systems, a concept of a layer such as a path, a line (M-section), or a section (R-section) and a way of use of an overhead are commonly set to these two transmitting systems.
FIG. 1 is a table showing a comparison of a way of use of each overhead of two kinds of synchronous digital transmitting systems. In the promotion of the overhead in each of the synchronous digital transmitting systems, the differences between the SONET transmitting system and the SDH one is only the following four points. First, the former system uses a C1 byte of a section overhead for specifying an OC-1 multiplex number of an OC-M signal, while the latter system uses the C1 byte of the section overhead for specifying an STM-1 multiplex number of an STM-M signal. The second different point is the way of use of the JO byte of the section overhead. The third different point is the way of use of the S1 byte of the line overhead. The fourth different point is the way of use of SS bits which correspond to fifth and sixth bits of an HI byte of a pointer.
The SDH transmitting system gives the C1 byte a multiplex number expressed at an STM-1 basis, while the SONET transmitting system gives the C1 byte a multiplex number expressed at an OC-1 basis. It means that both of the transmitting systems have respective transmission values. However, the SONET transmitting system is regulated to ignore the received C1 byte, while the SDH transmitting system has no regulation about the received C1 byte.
The JO byte is used as a section trace (R-section trace). The SDH transmitting system has a regulation about the way of use of the JO byte defined in the ITU-T G.707, while the SONET transmitting system has no regulation thereabout.
The low-order four bits of the S1 byte is used for a Synchronization Status Message indicating a network synchronous state. The code values of the four bits are respective in both of the transmitting systems.
In turn, the description will be oriented to the SS bits of a pointer. The pointers positioned at the H1 and the H2 bytes of the overhead are used each for indicating a head phase of a path. As shown in FIG. 2 which indicates the structure of a pointer portion of the overhead, both of the transmitting systems have respective ways of use for the SS bits of the H1 byte (fifth and sixth bits of the H1 byte). Concretely, the SDH system is defined so that the SS bits indicate an AU type and are defined as xe2x80x9c10xe2x80x9d, while the SONET system is undefined. In the SONET system, the undefined bit is xe2x80x9c0xe2x80x9d, so that the SS bits are made to be xe2x80x9c00xe2x80x9d.
The SONET transmitting system is arranged to ignore the SS bits in interpreting the pointer value, while the SDH transmitting system is arranged to contain the SS bits in the condition of interpreting the pointer value as described in the ITU-T G.783 ANNEX C(1996).
Herein, consider that a certain multiplex type transmitting apparatus is connected to the SDH system transmission path and the SONET system transmission path. For example, the fast transmission path employs the SONET system, while the slow transmission path employs the SDH system. At this time, the disadvantageous factor impacted on a main signal is only the difference of the SS bits among the foregoing four differences. Later, this factor will be discussed concretely. The slow transmission path is a signal transmission path in low bit rate of data before the multiplexing, and while the fast transmission path is a signal transmission path in high bit rate of data after the multiplexing. Hereinafter, the signal in low bit rate and the signal in high bit rate are called xe2x80x9cslow signalxe2x80x9d and xe2x80x9cfast signalxe2x80x9d, respectively.
Assume that the SONET system multiplexing apparatus provided with a pointer processing section receives the SDH system SS bits (xe2x80x9c10xe2x80x9d). In this case, the SS bits are ignored, so that the SS bits give no impact on the main signal. On the other hand, assume that the SDH system multiplexing apparatus provided with the pointer processing section containing the SS bits as the interpreting condition of the pointer value receives the SONET system SS bits (xe2x80x9c00xe2x80x9d). In this case, even if the received data is normal, the pointer processing section operates to detect a lost of pointer (AU-LOP) resulting from a mismatch of the SS bits. If an AU (Administrative Unit) detects an AU-LOP, an alarm signal (AU-AIS) is inserted into the AU. As a result, the received data disappears. Herein, the insertion of the AU-AIS means that the AU pointer and all the bits of a higher-order virtual container are made xe2x80x9c1""sxe2x80x9d.
On the other hand, the differences of the JO (C1) byte and the S1 byte do not have any impact on the main signal, such as disappearance of the received data.
As set forth above, the SONET system has a different way of use of the JO (C1) byte, the S1 byte, and the SS bits (fifth and sixth bits of the H1 byte) of the H1 byte of the pointer from the SDH system. If, therefore, any one of the SONET and the SDH transmitting systems is connected as a counterpart of the slow signal transmission path or the fast signal transmission path, each time the counterpart is connected, it has been necessary to at least select the SS bits of the SONET system or those of the SDH system to be transmitted by setting the SONET system signal or the SDH system signal from an operation system or a local craft interface. Or, in some cases, it has been necessary to select the JO (C1) byte and the S1 byte of the SONET system or those bytes of the SDH system in addition to the above-mentioned selection of the SS bits together.
In a case that the multiplex type transmitting apparatuses connected over a border of an international network have difficulty in determining that the counterpart of the slow signal transmission path or the fast signal transmission path is the SONET transmission system or the SDH transmission system, the transmission of the proper SS bits is disallowed to be assured. In some cases, the counterpart of the SDH system may induce the disappearance of data resulting from the mismatch of the received SS bits as mentioned above.
The present invention is invented in consideration of the aforementioned problems, and it is an object of the present invention to provide a multiplex type transmitting apparatus to be connected to any one of the SONET transmission system and the SDH transmission system counterparts for the slow transmission path or the fast transmission path without having to set the SONET system or the SDH system through the operation system or the local craft interface.
According to an aspect of the present invention, a multiplex type transmitting system includes a plurality of slow signal receive/transmit sections for receiving and transmitting a SONET system signal or an SDH system signal, a multiplex separation converting section, and a fast signal receive/transmit section for receiving and transmitting a SONET system signal or an SDH system signal. Each of the slow signal receive/transmit sections and the fast signal receive/transmit sections includes a receive processing unit on a receive side for receiving the SS bits (fifth and sixth bits of the H1 byte) SONET system or the SDH system signal received from the transmission path, an internal SS bits setting unit for setting the received SS bits to internal SS bits if the received SS bits is xe2x80x9c10xe2x80x9d or xe2x80x9c00xe2x80x9d or holding the previous state of the internal SS bits in any other case, a transmit processing unit on the receive side for setting the SS bits to xe2x80x9c11xe2x80x9d if the AIS is transferred, or unprocessing the SS bits or setting the SS bits to the internal SS bits or any value in any other case and then transmitting the resulting signal to the multiplex separation converting section, and a transmit processing unit on the transmitting side for keeping the SS bits as it is or setting the SS bits to xe2x80x9c11xe2x80x9d when the AIS is transferred with the signal from the multiplex separation converting section, or setting the SS bits to the internal SS bits in any other case and then transmitting the resulting signal onto the transmission path.
The multiplex type transmitting system according to the present invention is arranged as described above. Thus, though the SONET system has a different way of use of the SS bits of the H1 byte from the SDH system, when the SONET system interface of the apparatus is received with the SDH system signal or vice versa, the interface enables to identify the SONET system signal or the SDH system signal without any indication given from the operation system or the local craft interface and to transmit the proper SS bits to the counterpart.
Herein, the description will be oriented to the use of the multiplex type transmitting system closer to the border of the international network. FIG. 3 shows an overall appearance of (1) connecting the SDH system slow signal and (2) connecting the SDH fast signal to the multiplex type transmitting apparatus on the SONET system close to the border (frontier) between the SONET transmitting system as used in USA and the SDH transmitting system as used in Mexico, for example.
For (1) the connection of the SDH system slow signal, an SDH system multiplex type transmitting apparatus 250 is connected as a counterpart of a slow signal receive/transmit section (OC-12) 1-16 of the SONET system multiplex type transmitting apparatus 100. The SONET system multiplex type transmitting apparatus 150 (LTE: Line Terminating Equipment) is connected as a counterpart of another slow signal receive/transmit section (OC-12) 1.
For (2) the connection of the SDH system fast signal, a SONET system insertion separation multiplex type transmitting apparatus 103 and an SDH system insertion separation multiplex type transmitting apparatus 200 are connected as the counterparts of the fast signal receive/transmit sections (OC-192) 3 and 4 of the SONET system insertion separation multiplex type transmitting apparatuses 101 and 102 (ADM: Add Drop Multiplexer). The slow signal receive/transmit sections (OC-12) 1-3 and 1-4 of the insertion separation multiplex type transmitting apparatus 102 are connected as their counterparts to a SONET system multiplex type transmitting apparatus 150 and an SDH system multiplex type transmitting apparatus 250.
The fast transmission path between two LTEs not shown in FIG. 3 may be over the fast transmission path.
In turn, the LTE and the ADM shown in FIG. 3 will be described with reference to FIGS. 4 and 5. FIG. 4 is a functional block diagram showing an LTE multiplex type transmitting apparatus used for both the SDH system and the SONET system. As shown in FIG. 4, the LTE is composed of plural slow signal receive/transmit sections 1-1, 1-2, . . . , 1-16, a multiplex separating section 2, and a fast signal receive/transmit section 3. The signal receive/transmit section 1 or 3 includes an SPI (SDH Physical Interface) 30, a RST (Regenerator Section Termination) 40, an MST (Multiplex Section Termination) 50, an MSP (Multiplex Section Protection) 60, an MSA (Multiplex Section Adaptation) 70, and a HCS (Higher Order Path Connection Supervisory) 80, each of which have the corresponding function SPT, RST, MST, MSP, MSA, or HCS of the SDH system regulated in the ITU-TG.783 and the corresponding function of the SONET system as well.
FIG. 5 is a function block diagram showing an ADM type multiplex type transmitting apparatus used for both the SDH system and the SONET system. As shown in FIG. 5, the ADM includes a plurality of slow signal receive/transmit sections 1-1, 1-2, . . . , 1-16, a multiplex separating section 2, an insertion separating section 5, and fast signal receive/transmit sections 3 and 4. Like the LTE, each of the signal receive/transmit sections 1, 3, and 4 includes an SPI 30, a RST 40, an MST 50, an MSP 60, an MSA 70, and a HCS 80, each of which have the corresponding function of the SDH system regulated in the ITU-TG.783 and the corresponding function of the SONET system as well.
Next, the description will be oriented to the signal receive/transmit section of the LTE described in FIG. 4 and the ADM described in FIG. 5 with reference to FIG. 6. A signal transmitted from the transmission path side is applied to a pointer interpreting unit 111 of the MSA 70 in which the signal is interpreted as the pointer information and the information from an operating system 9. If necessary, the signal is converted in a pointer converting unit 112. The signal transmitted from the multiplex separation converting section 2 or the insertion separating section 5 is determined in an SS bits insertion determining unit 222 in which the information of an AIS identifying unit 211 of the MSA and the information from the operating system 9 are determined from the signal. An SS bits inserting unit 221 operates to insert the SS bits and then send out the resulting signal on the transmission path.